Theory Seminar on October 15, 4pm-5pm: Towards Practical Committee Sizes in YOSO MPC

Title:

Towards Practical Committee Sizes in YOSO MPC

Speaker：

Paweł Kędzior

Time:

October 15, Thursday 4pm-5pm

Venue:

Room 301B, Baichuan Building, Tsinghua Unversity

Abstract:

Secure multiparty computation on public blockchains must remain secure even when an adversary adaptively corrupts participants. The You-Only-Speak-Once (YOSO) approach addresses this through short-lived roles: participants send a message and then erase their state. However, earlier constructions required committees with thousands of members, posing a substantial obstacle to practical deployment. In this talk, I will present techniques that bring committee sizes down to around 100 participants in the parameter settings we study. These combine delayed identification of misbehaving parties using time-lock puzzles, publicly verifiable evidence that enables penalties, a selection procedure producing committees of a fixed size, and tighter probabilistic analysis. I will explain how these ingredients interact and discuss the resulting security and efficiency trade-offs.

The talk is based on joint work with Marcin Mielniczuk and Daniele Venturi, presented at CRYPTO 2026.

Short bio:

Paweł Kędzior is a PhD candidate at the University of Warsaw, supervised by Stefan Dziembowski. His research focuses on cryptographic protocols for distributed systems, including threshold and password-based cryptography, secure multiparty computation, and blockchain security. He is particularly interested in how formal cryptographic guarantees interact with accountability and economic incentives. His work has appeared at CRYPTO, ASIACRYPT, and AFT.